Automatic lighting system.



W. K. MCIVER.

AUTOMATIC LIGHTING SYSTEM.

APPLICATION FILED AFR. 26. I9I6.

Patented Dec. 24, 1918.

fyi

UNITED sTATEs PATENT oEEioE.

WILLIAM K. MCIVER, 0F ELGIN, ILLINOIS, ASSIGNOR T0 TI-IE VAN SICKLENCOMPANY, 0F ELGIN, ILLINOIS, A CORPORATION 0F ILLINOIS.

AUTOMATIC LIGHTING SYSTEM.

Application filed April 26, 1916.

systems and automatic controllers therefor, f

and the invention is particularly adapted for use with the lightingsystems of automobiles, or the like.

Some automobiles, particularly the less v -expensive ones, have lightingsystems in which the, current Jfor operating the 'head lights isreceived from the same magneto or generator which furnishes the currentfor ignition, and since the magneto is driven by the engine, eitherdirectly or indirectly, 1t Jfollows thatl the voltage impressed on thelighting circuit and the current flowing therein vary according to thespeed of the engine which drives the magneto. Thus, when the engine isoperating at a relatively high speed the voltage generated by themagneto is relatively high, and a corresponding high voltage isimpressed on the lighting circuit, thereby causing the lights includedin the circuit to burn brightly. l'lowever, when the engine is runningslowly, the voltage generated by the magneto is correspondingly low, sothat the voltage impressed on the lights is also low, thereby causingthem to give a dim and insufficient light.

The principal object ot this invention is to 'provide a lighting'system, especially adapted for use with automobiles, or the like, whichwill operate to cause a brilliant light to be produced, regardless ofthe voltage impressed on the circuit, or of the engine speed. A furtherobject is to provide improved means for automatically varying the numberof lights in the circuit in proportion to the voltage impressed on thecircuit. A still further object is to provide a lighting systemcomprising an electric circuit having lamps connected therein in series,in com bination with improved means for-'aut.omati cally varying thenumber of lights in operation. Another feature is the provision of aSpecification of Letters Patent.

in the operating circuit.

Patented Dec. 24, 1918.

serial No. 93,737.

lighting system, including a generating element of varying speed andvoltage in combination with improved means for controlling the number oflamps operated by this'y circuit in proportion to the speed of the generating element. A further ob] ect is to providean electric lightingsystem comprising a' plurality of lamps and a shunt circuit forrendering partoi' said lamps inoperative, in combination with improvedmeans for automatically controlling the operation of said shunt inproportion to the current flowing A further object is'to provide animproved automatic switch for automatically regulating the operation ofthe lighting circuit. provide an improved electro-thermal switchcomprising an expansible member adapted to control electric contacts forregulating the operation of the circuit according to the current flowingin the part oi' the circuit which is in operation. Still another objectis to provide an improved electro-thermal switch comprising adjustableparts adapted to vary the operation of the switch to suit differentoperating conditions.

These and other objects of the invention will appear more clearly fromthe following specification, taken in connection with the accompanyingdrawings, in which certain embodiments of the invention are illustrated.

In the drawings- Figure l is a diagrammatic view showing the circuitconnections of the lighting system, and the driving elements coperatingwith the electric generating device.

Fig. 2 is a sectional view, taken on the line 2 2 of Fig. 3, showing aplan View of the working parts of the electro-thermal switch.

Fig. 3 is a side elevation of the electrothermal switch, showing apartial section taken on the line 3 3 of Fig. 2.

Fig. 4 is a sectional view, taken on the line 4-1 of Fig. 3.

Fig, 5 shows detail views of the two movable contact. parts; and

Fig. 6 is a partial view, similar to Fig. 3, showing a modified form ofthe electrothermal switch.

Referring to Fig. l of the drawings, the electrical generating device10, which is preferably and usually an alternating cur- Another objectis to rent magneto, is shown operatively connected to an automobileengine, or the like, 11, through suitable driving connections,represented diagrammatica-lly at 12. @ne terminal of the magneto 10 isconnected to one line of the circuit, which in this instance isrepresented as the frame of the automobile, so that the connection isrepresented as a ground connection at 13. rll`he other terminal of themagneto is connected through the electric conductor 14, through amanually operated switch 15, with the improved electro-thermal switch16. lin an automobile lighting system of this kind the ignitionapparatus 17 may be connected by a conductor 18 with the conductor 14,and by a conductor 19 with the frame of the machine, or the ground whichforms the return circuit. 'llhe circuit from the automatic switch 16 isnormally through parallel or shunt conductors 20 and 21 which lead tosuitable terrninals of the 'head lights, or other electric lamps to beoperated by the lighting circuit. lln this instance the electric lamps22 and 23 are represented as right and left head lights, respectively,of an automobile, being contained within the usual reflecting casings24. rllhe two lamps 22 and 23 are connected in series by the conductor25, and the terminal of the lamp 23, opposite said conductor, isconnectedto the return circuit, as shown by the ground connection at 26.rEhe conductor 20, leading from the automatic switch 16, is connected tothe conductor 25 at a point' between the lamps, andthe conductor 21 isconnected to the terminal of the lamp 22 opposite that to which theconductor 25 is connected.

ln the operation of the lighting system, if

the shunt 2O is rendered inoperative, the current flowing through theconductor 14 and through the automatic switch 16 will pass through theconductor 21, and lthence through the lamps 22 and 23 in series to thereturn circuit, which is represented by the frame of the automobile. Itwill be seen that the conductor 2O has relatively low resistancecompared. with thcresistance of the parallel circuit, consisting of theconductor 21 and the lamp 22, and when the shunt is electricallyconnected to the conductor 14 through the switch 16, the current flowingin the circuit will pass through the shunt to the lamp 23, while thelamp 22 will be inoperative, as hereinafter more fully described. Thepurpose of the invention as applied to the particular embodimentillustrated is to provide means for causing both of the lamps to beoperated when the magneto is driven at a relatively high "speed, so thatthe corresponding voltage impressed upon the circuit will be,sufficiently high to cause both of the lamps to burn brightly; and afurther feature is to provide means for rendering one of the lampsinoperative when the ,engine is i ,eeen/iv running at a relatively lowspeed, so that the voltage developed by the magneto will be impressedupon one light only, thereby causing said light to burn brightly.

The foregoing advantages are obtained in connection with the otherfeatures of the lighting system by means of the automaticelectro-thermal switch 16. This automatic switch embodies an insulatingbase or plate 30, constructed of prepared wood, porcelain, or otherinsulating material not materially affected by moisture, oil, grease, orordinary weather conditions. 'lhe end portions of this plate areprovided with integral, transversely-extending lugs 31, the end portionsof which are semi-circular in contour. Each of these lugs is providedwith an aperture 32 adapted to be engaged by a screw 33, by means ofwhich the base is secured to a supporting member 34, which may be thedash, or other suitable part of the automobile, for instance. A cap orcasing 35, formed preferably of stamped metal, or the like, isadapted-to be inserted between the insulating base and the supportingmember 34, and

' ts closely the lateral walls of the insulating base. The lugs 31 areprovided with undercut shoulders 31, which permit the wall 35a of thec'ap to lie Hush with the end walls of the lugs, and the lateral wallsof the base 30 are spaced apart a lesser distance than the width ofeither lug, so that the lateral walls 35k of the cap will lie Hush withthe corresponding edges of the lugs. lt will be seen that the shoulders31a and 31". thus formed at the edges of the lugs, are adapted to holdthe cap 35 in rigid position with respect to the base, so that the capcompletely incloses the chamber 36 formed between the base and the capand between the end lugs. r[he edges 35n of the lateral walls of the capare in-turned, as shown, for instance, in Fig. 4, to fit closely thesimilarly beveled edges of the base, so that when the cap is inserted inposition on the base the edges of the cap will snap over the edges ofthe base, and thus hold the parts in relatively fixed engagement.

In the embodiment of the automatic switch shown in Figs. 2 and 3.abracket 40 is secured to the insulating base 30 at one end thereofwithin the chamber 36, the base bcing provided with a countersunk seat41, which is adapted to conform to the contour of one of the parallelflanges 40a of the bracket. This bracket is secured in the positiondescribed by means of the screw 42. which passes through the lowerflange 40a and through the insulating base 30, being secured in positionby means of a lock nut 43. A pair of washers 44 are placed on the screwadjacent the lock nut, and a nut 45, engaging the screw, is adapted foruse in clamping an electric conductor between the washers, whereby thescrew and parts carried thereby serve as a binding post for use informing an electric connection with the conductor 14 of the lightingcircuit. Adjacent the other end of the chamber 36 another bracket 46 isseated in a suitable recess 47 formed in the upper wall of theinsulating base, held in place by screw 48 being engaged at its lowerend by a lock nut 49, washers 50, and clamping nut 5l, which coperatewith the screw to form a binding post, by means of which an electricconnection may be formed with the conductor 21 of the lighting systemabove described.

The bracket 46 comprises an upwardly extending flange or post 46a, whichis provided -with a relatively small transversely-extending slot adaptedto be engaged by a thermally expansible wire 52, which is passed throughthe slot and around the post, and then soldered or otherwise secured infixed position. The opposite end of this expansible wire is wound uponthe drum or shaft 53, which is provided with'reduced ends suitablyjournaled in the flanges 40a of the bracket 40. A worm gear 54 is fixedon the shaft or drum 52, and arranged to mesh with thetransversely-extending worm or screw 55, which extends through thevertically projecting flanges 40b of the bracket 40, and through asuitable slot or aperture in the wall of the casing 35, so that the head55a thereof may be engaged by a screw driver, or the like, at theoutside of the casing to eii'ect the rotation thereof and'correspondingrotation of the worm gear, which will operate to wind the expansiblewire on the drum, and thereby adjust the tension of the wire, or correctany stretching thereof. The extremity 55b of the worin 55 is rotatablymounted on the bracket 40, and has secured thereto a nut or Washer 55,which serves to secure the worm in position. The expansible wire'52 hasa relatively small cross sectional area, and it is formed preferably ofsterling silver wire, although other suitable material of low specificresistance may be used if desired. l

At a point between the binding screws 42 and 48 there is mounted a thirdbindingy post 56, carrying a lock nut 57, washers 58, and clamping nut59, by means of which an electrical connection may be formed with theshunt conduftor 20 of the lighting system above described. Each of thebinding posts is preferably provided with suitable means, su'h as a lug65 engaging a groove in the wall of the corresponding aperture in thebase, whereby rotation of the binding screws is prevented when theclamping nuts are being tightened. A spring contact member60 is clampedbeneath the head of the binding post 56. being inserted in a suitablerecess formed in the wall of the insulating base. A second spring blade61', of relatively greater length than the spring con- Vis secured tothe base by means of a screw 63, which passes through the aperture 64formed in the enlarged extremity of the blade, and through a suitableaperture in the base, being engaged at its outer end by a nut 66. Theblades or arms of the resilient members 60 and 61 are directed in thesame direction parallel to the expansible Wire 52, and the extremitiesof these blades carry contacts 60a and 61a, respectively, formedpreferably of platinum, or the like, which are adapted to coact witheach other when the expansible wire is in its normal taut condition andwhen the spring blades are in corresponding depressed positions. Theextremity of the spring ,blade 61, adjacent the platinum' Contact, 61a,is bent transversely to form a projection 61", which isapertured at 61cto be 'engaged by the thermally expansible wire.

4The movable resilient members 60 and 61, which are formed preferably ofspring bronze, are so constructed and proportioned that the contacts60a-and 61a willremain in electrical connection through a considerablevrange of movement of the springs correof the resilient spring 61 whenthe wire 52 expands under the inuence of a current passing therethrough;but the construction and arrangement is such that after'a predeterminedexpansion of the wire the spring 61 will pass out of Contact with thespring 60, and thereby break the electricalv connec-v tion to theconductor 20, which is in the circuit therewith. The point at which thespring 61 breaks contact with the movable contact member 60 may bevaried by means of the worm and worm gear, which operate to vary thenormal tension of the expansible wire. If the expansible wire isstretched relatively tight, the springs will v be depressed in acorrespondingly increased degree, so that they will remain in contactthrough a greater range of movement than in the case where theexpansible wire has an initial upward lexure under the influence of thespring 61 before it is expanded under the influence of a current passingtherethrough. l

Instead of varying the point of separation of the spring 61 vwith themovable spring contact member 60, by means of the worm and worm gearabove described, I may em.

stretched taut at working atmospheric temperature when the parts of thedevice are initially assembled, in which condition it will remain whenunheated, since it has no appreciable tendency to stretch. The springblades 60 and 6l are mounted and constructed as in the embodiment abovedescribed, but a metal plate 72 is mounted beneath the lock nut 57 ontthe binding screw 56, and an adjusting screw 73 threadedly engages thisplate and passes through the insulating base to coact continuously withthe surface of the blade 60 adjacent the binding screw by means ot'which said blade is secured in position. This adjusting screw may bemanipulated to vary the pressure which it exerts upon the under side ofthe blade 60, so as to alter the normal position which said blade tendsto assume by virtue of its resiliency when not restrained by means otthe expansible wire 52. f 'llhis adjusting screw serves, in edect, tovary the attachment of the blade 50 to the insulating base, so that.

the normal unrestrained position which it assumes by virtue of itsresiliency may be varied to vary the point at which the movable contact60a, carried by the blade 60,

` passes out of engagement with the contact 61a carried by the blade 6l.

F rom the foregoing description it will be seen that the binding post t2is connected to the conductor M, the binding post 56 to the conductor20, and the binding post 48 to the conductor 21, so that a circuit maybe formed from the binding post 42 through the entire length' of theexpansible wire 52 to the binding post 48, and thence through theconductor 2l, light 22, conductor 25, and light 23 to the groundconnection 26, which represents the return circuit; or when the springcontact member 60 is in engagement with the contact 61a a' shuntconnection will be formed through the conductor 20 around the lamp 22,so that said lamp will be rendered inoperative. `When the spring bladesare in contact the current Hows through the portion 52a only of thethermally expansible member, and as this portion of the expansible wireexpands the wire will be given a transverse eXure by the resilientspring 61. As the wire bends transversely and the contact 61a movestherewith, the Contact v6ft, carried by the spring 60, w1ll remain inelectrical connection with the contact 61EL during a considerable rangeof movement; but when the current through the portion 52a of theexpansible wire has increased sufiiciently to cause a transverse idexureof the wire 4which carries the contact 61a beyond the limit of movementof the spring member 60, the connection through the spring member of theconductor 2() is broken, and the current then flows through the entirelength of the wire, and thence through .both of the lamps in series. Thecurrent then continues insane-r to How through both ot the lamps inseries until the voltage drops suflciently to cause a contraction of theexpansible wire of such extent as to reestablish the connection with theshunt circuit.

The point at which the spring blade 61 is connected to the wire is solocated that the expansion of the portion 52* of the wire by the currentwhich Hows therethrough when one lamp is in operation, at the instantwhen the shunt connection is broken, will edect a transverse exure ofthe wire, substantially the same or slightly less than the transversedenure which is caused by the current which Hows through the entire wirewith two lamps in operation at the instant after the shunt connection isbroken. llmmediately after the shunt connection is broken the currentflowing through the entire enpansible wire, and -through the two lampsin series, is somewhat less than the current which previously tlowedthrough the portion 52a with one lamp only in operation; but theflow ofthe reduced current through the entire wire might cause a greater or aless transverse HeXure of said wire than would be caused by the flow ofthe increased current through a part of said wire, unlessl the point otcontact of the spring 6l with the wire be properly located and it hasbeen found, in the embodiments o the invention which have been employed,that the portion '52a of the wire should have a length substantially 31%of the total length of the wire measured between the post 46a and thedrum 53, or bracket 70, to which the other end of the wire is connected.The point of contact of the wire with the eX- tremity of the springblade 6l may be varied through a considerable range by bending thetransversely projecting part 6lb of the spring blade in a directionparallel to the length of the expansible wire, thereby varying the pointat which the wire engages the v walls of the apertures 61e; and in orderto increase the possible range of this adjustment the aperture 20c ispreferably located a relatively great distance from the adjacenttransverse portion of the spring blade.

By means of the construction just described it is possible to locateaccurately the point of connection ofthe contact with the intermediatepoint of the expansible wire, so that the expansion of the part of thewire through whichthe current flows when the shunt is closed willproduce substantially the same transverse movement of the wire at saidintermediate point as is caused by the flow of current which takes placethrough the entire expansible wire immediately after the shuntconnection is broken. This is an important feature of the construction,since it overcomes the possibility of an intermittent action of theswitch, which might result if the transverse movement of the entirewire-due to the current of that part of the expansible wirel throughwhich the current of the shunt circuit flows, until the voltageimpressed on ythe circuit and corresponding current liowing through theyentire wire have decreased suliiciently t0 cause the contact 61a torengage the contact 60a. In practice, it is found that when the switchoperates to break the shunt connection, the contact 61a moves at once aconsiderable distance away from the contact 60a,due to the fact that theportion 52a of the expansion member is at first heated to a higherdegree than the remainder of said member, owing to the relatively largercurrent which has previously passed therethrough with the contactsclosed; but as the portion 52E-contracts, so that its expansion per unitof length is the same as that of the remaining portion, the contact 61aslowly moves back toward the contact 60@L but stops in a position spacedfrom said contact, provided the voltage has not fallen below the valuewhich caused the shunt connection to open. It will be seen that thisoperation causes a quick breaking of the shunt circuit which preventsarcing.

If the voltage and corresponding current continue to increaseimmediately after the shunt connection is broken, the expansible wirewill continue to move transversely under the influence of the springblade 61, and the brilliancy of the two lights operated by the circuitwill continue to increase accordingly within limits depending upon theirform and principles of operation. lVhen the speed of the automobileengine decreases. and a corresponding drop in voltage takes place, theexpansible wire will contract until it finally restablishes a connectionwith the spring contact member 60, thereby closing the shunt around apart of the circuit and rendering that part. inoperative. If the voltagestill further decreases thereafter, the wire will continue to contract,thereby depressing both 0f the springs 60 and 61, which will movetogether while. being depressed, while at the same time`VV maintainingthe connection through the shunt.

The point of connection of the Contact with an intermediate part of theexpansible wire will depend for its location upon the number of lamps inthe circuit, their relative capacities, and the number of lamps to beshunted by the shunt circuit, so that in somo instances it may be4necessary to locate the point of contact differently than is hereindescribed for lighting systems including two automobile head-lights ofsimihas been located at a point spaced from the lar size and rating. Theproper size of the expansible wire to be used will also depend upon thecurrent required to operate the incandescent lamps, or other translating-devices in the circuit. In certain embodiments of the invention whichhave been employed in connection with an automobile lighting systemincluding two incandescent lamps rated at 6 amperes and 12 volts, asterling silver expansible wire ,having a diameter of approximately fivethousandths of an inch has been used with satisfactory results, and thepoint of connection of the shunt with the eXpansible wire end of thewire a distance substantially equal to 31% of the length of the wire.The eXpansible wire should of course be of such cross section andspecific resistance that it will expand properly under the influence 0fthe currents in the circuit for which the switch is designed. Thespecific resistance should preferably be relatively low in order thatthe wire may be reduced in size to secure aV relatively large radiatingsurface per unit of cross-sectional area, thereby causing it to respondquickly to changes in voltage and corresponding changes in current.

If it be found that the connection of the expansible wire with thecontacts 60a is broken before the voltage has increased sufficiently tocause both of the head-lights tov burn with the desired brilliancy, theworm and worm gear can be adjusted to increase 100 the initial tensionof the expansible wire: or if the form of switch shown in Fig. 6 isused. the adjustment screw 73 may be manipulated to vary the limitingposition which the spring blade 6() assumes by virtue 105 of itsresiliency, so thatthe contacts 60a and 61*l will remain in engagementwith each other through a greater range of movement of the expansiblewire, that is, until the voltage has increased to a greater extent thanin the instance first supposed. 'It will be apparent that it is anadvantage that these adjustments be made from the outside of the casingby manipulating the worm or the adjustment screw. If desired, the meansfor adjusting the tension of the wire and for varying the normalposition of the contact blade 60 may be combined in one structure, sothat both adjustments may be employed for'the purpose described.

It will be apparent that by means of this invention a lighting system ofthe class described may be operated to give an efficient light atsubstantially any voltage and any speed of the driving element. When thespeed is relatively high both lights will burn brightly, and when thevoltage drops with a fall in speed one lamp is automatically shunted sothat the other light burns brightly at the reduced voltage. Theoperation of the circuit does not operate at any time to overload themagneto, since the cur-r which is in operation constant-ly during theoperation of the circuit, is located at the lett hand side of thevehicle, on which side the driver sits and next to which other vehiclespass. Where an alternating current magneto is used, the improvedthermo-electric controller of this invention is of great advantage,since its operation is not affected by changes in frequency of thecurrent which take place as the speed changes, and it therefore operatesaccurately and eiiciently while other circuit-interrupting deviceshaving inductance or capacity would be inoperative. Because of theabsence of inductance and any appreciable capacity in the electrothermalswitch, it will be seen that the connection thereof in the circuit doesnot operate to alter or disturb thel wave form of the alternatingcurrent generated by the magneto or other generator.

Although lt have shown and described a particular embodiment ot theinvention for purposes of illustration, it will be under stood that itmay be embodied in other forms without departing from the scope thereofas defined in the appended claims.

I claim 1. ln a system of the class described, work circuit including aplurality of translating devices connected in series, a shunt forrendering a part oit said devices inoperative, and a switch comprisingan electrothermal wire connected in said circuit for controlling theconnection of said shunt, the expansion of a part of saidelectro-thermal wire hy the action of the current passing therethroughbeing adapted to disconnect said shunt and cause the current to passthrough the other part of said electrothermal wire. 2. llna lightingsystem, a circuit including an expansible conductor and a plurality oflamps in series, a shunt normally connected to an intermediate point ofsaid conductor and around a part of the lamps to render Asaid partinoperative, andmeans actuated by the expansion of a part of saidconductor due to the current flowing therein tor automaticallydisconnecting the shunt.

3. ln a lighting system, a circuit including an expansible conductor anda plurality of lamps in series, a shunt normally connected to anintermediate point of said conductor and around a part of the lamps torender said part inoperative, and means actuated by the expansion of apart of said lconductor due to the current flowing therein forautomatically disconnecting the shunt, the restablis'hment of theconnection of said shunt with said conductor being governed by theexpansion of the entire conductor due to the current which flows thereinwhen the shunt connection is broken.

e 4. lin an electric lighting system, a circuit including an expansibleconductor and a plurality of lamps in series, a shunt normally connectedto an intermediate point of said conductor and around a part of thelamps to render said part inoperative, means tending to produce atransverse fleXure of said conductor as the same expands due to thecurrent Howing therein, and a Contact adapted to break connection withsaid conductor to open the shunt after a predetermined movement ot theconductor due to the expansion caused by current ilowing through theshunt, the flow of current aittersaid shunt connection is broken beingthrough. the entire eXpansib-leconductor and through all of the lamps inseries 5. ln an electric lighting system, a circuit including aneXpansible conductor and a 'of said conductor and around a part of thelamps to render said part inoperative, means tending to produce atransverse HeXure of said conductor as the same expands due to thecurrent flowing therein, and a Contact adapted to break connection withsaid conductor to open the shunt after a predetermined movement ot' theconductor due to the expansion caused by the current which flows throughthe shunt, the How of current after said shunt connection is brokenbeing through the entire eXpansible conductor and through all of thelamps in series, said conductor being adapted to reestablish aconnection with said contact after a predetermined decrease of thecurrent flowing through the entire conductor.

6. ln an electric lighting system, a circuit including an expansibleconductor and a plurality of lamps in series, a shunt normally connectedto an intermediate point ot said` conductory and ,around a part of thelamps to render said part inoperativemeans tending to produce atransverse flexure of vsaid conductor as the same expands due to the imthrough the entire eXpansible conductor and through all of the lamps inseries, said co-nductorbeing adapted to restablish a connection withsaid contact. after a predetermined decrease o the' current flowingthrough the entire conductor, the point of connection ot said conductorwith said shunt being located between the ends of said conductor at sucha point that the movement ont the conductor owing to the expansion of apart thereof by the current which flows through the shunt issubstantially the same as the transverse movement caused by `theexpansion of the entire conductor by the current which 'flowstherethrough at the instant after the connection with the shunt isbroken.

7. In a lighting system, a circuit including a plurality of lamps and anexpansible conductor in series, said conductor being supported at itsextremities, means acting to produce a. transverse movement of saidconductor at an intermediate point thereof when it expands owing to theCurrent passing therethrough, a movable contact adapted to form anelectrical connection with said conductorat said intermediate pointthroughout a predetermined movement of said conductor and to breakcontact therewith after such predetermined movement, and a shuntconnected to said movable contact and around a part of said lamps in thecircuit to render said part 0f the lamps inoperative when the yshunt isconnected to the intermediate point of said conductor.

8. In a lighting system, a circuit includinga plurality of lamps and anexpansible conductor in series, said .conductor being supported aty itsextremities, means acting to produce a transverse movement of saidconductor at an intermediate point thereof when it expands owing to thecurrent passing therethrough, a movable contact adapted to form anelectrical connection with said conductor at said intermediate pointthroughout a .predetermined movement of said conductor and to breakcontact therewith after such predetermined movement, a shunt connectedto said movable contact and around a part of said lamps in the circuitto render said part of the lamps inoperative when the shunt is connectedto the intermediate point of said conductor, and means to vary thedegree of expansion of said conductor required to effect the breaking ofthe electric connection with said movable contact. I

9. In a lighting system, a circuit including a plurality of lamps and anexpansible conductor in series, said conductor being supported at itsextremities, a resilient member operatively connected to an intermediatepart of said conductor and arranged to cause a transverse movement ofsaid conductor at the point of connection owing to the increase inlength of said conductor due to the passage of current therethrough, aspring contact blade arranged to form an electrical connection with saidconductor at said point of connection and to move with said resilientmember through a predetermined range of movement, the connection of saidspring contact blade with said conductor being broken after saidintermediate part has moved beyond the limiting position which saidspring contact blade can assume by vrtue of its resiliency.

1Q. In a lighting system, a circuitincludingv'a plurality of lamps andan expansible conductor in series, said conductor being supported at itsextremities, a resilient member operatively connected to an intermediatepart of said conductor and arranged to cause a transverse movement ofsaid conductor at the point of connection owing to the increase inlength of said conductor due to the passage of current therethrough, aspring contact blade arranged to form an electrical connection with saidconductor at said point of connection and to move with said resilientmember through a predetermined range of movement, the connection of saidspring contact blade with said conduct-or being broken after saidintermediate part has moved lbeyond the limiting position which saidspring contact blade can assume by virtue of its resiliency, andadjustable means .coacting with said spring contact blade for varyingthe limiting position which it assumes by virtue of its resiliency.

11. In a lighting system, a circuit including a plurality of lamps andan expansible conductor in series, said expansible conductor beingsupported atits extremities, a leaf spring bearing on an intermediatepart of said conductor and tending to cause a transverse flexure of'saidconductor as the same expands duev to 'a current passing therethrough, aspring contactl having a part adapted to coact with said leaf spring andto move therewith through a predetermined range of movement of said leafspring, and a shunt connected to said spring contact and around a partof said lamps to render said parts of said lamps inoperative when saidspring contact is in electrical connection with the eXpansible conductorthrough said leaf spring.

12. An electro-thermal switch comprising i an insulating base,`.supportson said base, a thermally expansible member stretched betweensaid supports, a spring bearing on an intermediate part of saidexpansiblel an insulating base, an expansible conductor having itsextremities secured to said base, means for forming an electricalconnection with the extremities of said vexpansible conductor, wherebythe latter may be included in an electric circuit, resilient means en#gaging an'intcrmcdiatc part of said conductor and 'tending to cause atransverse dexure thereoie as the length of said conductor increases dueto the current passing therethrough, a movable contact adapted to torman electrical connection with saidl intermediate part of said conductorand to maintain said connection throughout a predeterminedrange ofmovement of said conductor, and means for forming an electricalconnection with said movable contact whereby said contact member may beincluded in a branch circuit.

14E. An electro-thermal switch comprising an insulating base, anexpansible concluetor having its extremities secured to said base, meansfor including an eXpansible conductor in an electric circuit, resilientmeans engaging an intermediate part of said vconductor and tending tocause atransverse HeXure thereof as the length of said conductorincreases due to the current passing therethrough, a movable contactadapted to form an electrical connection with said intermediate part ofsaid conductor and to maintain said connection throughout apredetermined range of movement of said conductor, means for forming anelectrical connection with said movable contact whereby said contact maybe included in a branch circuit, and means to vary the transversemovement of said conductor required to break the electrical connectionwith said movable contact.

15. An electro-thermal switch comprising an insulating base, supportingmeans mounted on said base, a thermally expansible conductor stretchedbetween said supporting means, a spring blade mounted on said base andoperatively connected at its free end with said conductor at anintermediate point thereof, a spring contact blade mounted on said baseand adapted to contact at its tree end with said irst-nam'ed springblade to ei'ect an electric connection with said conductor at saidintermediate point, saidv spring contact blade being adapted to movewith said first-named spring blade as said conductor expands due to acurrent passing through a part thereof nasser? and to break contacttherewith when said `rst-named spring blade moves beyond the normalposition which said spring contact blade tends to assume by virtue oitits resiliency, and means connecting said eXpansible conductor and saidspring contact blade in an electric circuit.

16. An electro-thermal switch comprising an insulating base havingtransversely extending lugs adapted Vto engage a support, a casingarranged to t over said base to form a chamber between said lugs,supports mounted on said base in said chamber, a thermally expansibleconductor stretched between said supports, a resilient member mounted insaid chamber and bearing against an intermediate part bi saiderrpansible member, a movable contact carried by said base and adaptedto form an electrical connection with said eXpansible meme ber until thelatter has moved by expansion beyond the limit of movement ot saidmovable contact, and means to include said movable contact and saidexpansible member in an electric circuit.

l?. An electro-thermal switch, comprising an insulating base havingtransversely extending lugs adapted to engage a support, a casingarranged to lit over said base.

to form a chamber between said lugs, supports mounted onl said base insaid chamber, a thermally expansible conductor stretched between saidsupports," a resilient member mounted in said chamber and bearingagainst an intermediate part oi said eXpansible member, a movablecontact carried by said base and adaptedsto form an electricalconnection with said expansible member until the latter has moved byexpansion beyond the limit of movement oit said movable contact, meansto include said movable contact and said eXpansible member in anelectric circuit, and means operable from the outside ont said chamber'for regulating the operation ot said switch.

lln testimony whereof, ll have subscribed my name.

WTLLMIAM K., MollVER.

